Connection devices, of the initially named type, are used for the connection of all types of torque transmitting components to associated shafts or hollow shafts. Conventional connections of this type are used, for example—but by no means exclusively—in the assembly of torque levers or control arms on torsion rods or stabilizer devices. One field of use, merely by way of example, is the area of shock and vibration absorbing suspension of motor vehicle driver's cabins, especially for trucks and similar heavy-duty trucks, in order to uncouple the driver's cabin with respect to vibrations and motions of the vehicle chassis in this manner.
Because the spring rates of the chassis springs in heavy-duty trucks are inevitably high, due to the heavy vehicle loads, unevennesses in the road surface or even vibrations and structure-borne noise, resulting from axles and the drive train, are still transmitted, to a considerable extent, to the chassis via the axle spring mounting. In order to minimize the transmission of such continuous shocks and vibrations to the driver's cabin, and thus to driver's workplace in terms of ergonomics and occupational safety, driver's cabin suspensions have been developed in which the driver's cab or cabin is supported by vehicle chassis using a separate suspension system.
Such suspension systems, for the driver's cabin, can be designed with lower spring rates and softer shock absorbers than the axle suspension due to the much lower weight of the driver's cabin in comparison to the weight of the vehicle, which is why unevennesses of the road surface or vibrations originating from the drive train or axles of the vehicle can therefore be isolated or kept away from the driver's workplace, to a significantly greater extent, due to such softer cabin suspension systems.
Such suspension devices for driver's cabins have a complex design, particularly with increased requirements on supporting transverse forces or kinematics, for example the suppression of pitching and rolling and sideways control. Thus, along with the actual spring and absorber elements similar to axle suspensions of motor vehicles, roll stabilizers in particular must be provided, with which the undesired, lateral roll of the driver's cabin relative to the chassis of the vehicle can be reduced.
With suspension devices for driver's cabins, according to the prior art, for example in the case of travel on inclines or in curves, but also for example in the case of road surface unevennesses on one side, roll stabilizers, in the form of torsion rods or stabilizer hollow shafts, are provided for roll stabilization, whereby the spring compression travel of the left and right suspension elements of the driver's cabin, relative to the direction of travel, are coupled together to a certain degree.
In order to introduce the forces, torques and motions of the vehicle cabin into the roll stabilizer, and for the purpose of the guidance of the vehicle cabin in the longitudinal and transverse direction, generally torque levers or torsion limbs are attached to both axial ends of the roll stabilizer, whose end located away from the stabilizer is connected to the vehicle cabin by means of a bearing, while the end of the torque lever near the stabilizer is connected to the roll stabilizer. The bearing of the torque levers, that is rigidly connected to the chassis, is represented here either by the stabilizer itself, or an additional bearing point is disposed at the end of the torque levers that close to the stabilizer, which serves for the movable connection of the torque levers to the chassis, and for introducing the reaction forces, occurring during rolling motions, into the chassis.
Conventional connection devices, particularly between roll stabilizers and torque levers assigned to them, are exposed to very high stresses during their service life. This is especially true when, for example, for reasons of weight reduction with simultaneous increase of the torsional rigidity, torque rods or stabilizer shafts for roll stabilizers are designed in the form of comparatively thin-walled torsion tubes or hollow shafts.
It is known from the prior art to weld or to press connect, for example, the torque levers to the torsion tubes for the torque transmitting connections of such torsion tubes or hollow shafts to corresponding connection components, such as torque levers. In both cases, however, a connection produced in this manner, between the torque lever and the torsion tube, represents a highly stressed potential weak point.
With a welded connection between the torque lever and the torsion tube, this is linked above all to the heat introduced during welding and with the associated microstructural changes, as well as to the unavoidable occurrence of notch stresses. Pure press connections, between the torsion tubes and torque levers, can be established by comparatively gentle cold forming; however, they often fail to attain the necessary service life in the case of the strong forces and high torques that occur. This is also true when, for the purpose of increasing the torque that can be transmitted, a cross sectional shape differing from the circular shape is selected for the hollow shaft in the area of the connection to the connection component.
In particular, with the use of comparatively thin-walled torsion tubes for weight reasons, this is linked to the fact that the tube wall can transmit only limited pressing and shearing forces into the torsion tube in the area in which the force is introduced. For this reason, interference fits, for example, between the hollow shaft and the connection component cannot be implemented with the fixed press fit necessary for transmitting high torques. When the comparatively weak specific forces that can be transmitted are exceeded, the tube wall will therefore separate in the area of the press fit of the torque lever, or the tube wall can be pressed in, which leads to the subsequent failure of the tube cross section.
For overcoming this problem, the document DE 10 2005 056 878 B4 proposed to forgo a weld connection, between the hollow shaft and the torque lever, and to avoid the disadvantage of a press connection, in that after producing the press connection, between the hollow shaft and the torque lever, a plug is driven into the area of the press connection which supports the relatively thin-walled tube in this area, and thus is intended to guarantee the permanent, reliable transmission of high torques.
Despite this proposed improvement, the possibility disclosed in this publication for connecting hollow shafts to connection components is limited to specific intended uses, or requires possibly a series of additional component assemblies or parts for implementing further functions, such as are necessary, particularly however not exclusively, in the case of roll stabilizers for driver's cabs. Among these functions, or objectives, are particularly providing pivot points and bearing points for the bearing blocks disposed on the driver's cab and on the chassis, or for further component assemblies, for instance, for spring/absorber elements for suspension of the driver's cab.
The field of application of customary connection devices also extends further to roll stabilization and axle guidance in vehicle axles, particularly utility vehicles. For roll stabilization of vehicles axles, anti-roll stabilizers, consisting mainly of solid material and bent from one-piece, are used in the prior art, which have a corresponding high mass, especially in heavy utility vehicles, and whose degree of material utilization is extremely unfavorable with respect to the intended twisting and torsional rigidity. The replacement of the massive anti-roll stabilizers by bulky, comparatively thin-walled and thus lighter weight hollow shafts has to date often been unsuccessful because of the problematic connection techniques between such hollow shafts and the torque transmitting connection components, such as torque levers. Further, with such anti-roll stabilizers for vehicle axles, it is also desired to confer, along with the actual function of roll stabilization, further functionalities or axle guiding tasks to the stabilizer, in order to obtain constructively simpler, more robust axle suspensions with lower mass.